Pen type drug delivery devices have application where regular injection by persons without formal medical training occurs. This is increasingly common among patients having diabetes where self-treatment enables such patients to conduct effective management of their diabetes.
For good or perfect glycemic control, the dose of insulin or insulin glargine has to be adjusted for each individual in accordance with a blood glucose level to be achieved. The present invention relates to injectors, for example hand-held injectors, especially pen-type injectors, that is to injectors of the kind that provide for administration by injection of medicinal products from a multidose cartridge. In particular, the present invention relates to such injectors where a user may set the dose.
A user undertaking self-administration of insulin will commonly need to administer between 1 and 80 International Units.
In medication management, compliance i.e. the degree to which a patient follows medical instructions and protocols, is often of extreme importance. In relation to injection of medicaments, one key aspect of determining the compliance is determination of the actual dose of the medication injected. Another key aspect is determination of the set dose. Accordingly, it is desirable to provide medication delivery devices and/or systems with dose quantity identification systems.
Systems known in the art comprise a detector for providing a signal indicative of an amount of an ejected dose of a drug such that the user may keep a log of the injection history. This kind of system provides information about the actual dispensed dose. However, there is no information available to indicate that the ejected dose is equal to the intended dose. A second sensor would be required to implement this feature.
Other systems known in the art comprise a doseable quantity identifier comprising a rotational matrix and a sensor, wherein a controller circuit interprets the sensed data to determine a quantity of medicine to be delivered. The rotational matrix is often implemented to rotate during dose setting and injection. E.g., the matrix is arranged circumferentially on a sleeve providing absolute positional encoding for one revolution/rotation only. To distinguish between dialing a dose and injection, the processor uses input form an additional separate switch. The switch may be mechanically coupled to a dose button, such that pressing the dose button closes the switch, e.g. via slider, or a barrel having a ramped region. However, implementation is rather complex requiring a dose quantity identifier and a switch arrangement. Both features need to be implemented reliable and resistant against malfunction as well as manufacturing tolerances.